The mouse pads can be to porus, in other words, to foamy, they can leak air into the barrel. Just go to bunnings and pick up a rubber gasket(usually black or orange) and get the thickets one you can find.

Check the pipe, it should have PNXX on it, the XX is where a number will be, like mine is PN12, PN12 = Pressure Number 12 BAR, which is around 175psi.